Various types of locking devices have been designed for a multitude of purposes. In the field of utility hitches, U.S. Pat. No. 3,605,457 to Foster and U.S. Pat. No. 3,139,291 to Geresy disclose trailer hitch locking devices that are used to lock a trailer hitch tongue to the ball of a conventional type trailer hitch.
Another type of device, called a pin lock or a coupler lock is generally used for locking together the central hitch member and outer hitch member of telescoping type utility hitches. In this type of utility hitch, the central hitch member fits telescopically into an outer hitch member. Apertures through both hitch members are aligned so that the pin lock can be inserted through the apertures to hold the central hitch member within the outer hitch member. The pin lock is locked onto these members to prevent removal of the pin, so that the vehicle that is connected to the hitch member, such as a trailer, cannot be stolen.
U.S. Pat. No. 5,540,065 to Wyers is an example of such a prior art pin locking device. The disclosed pin locking device includes a rod having a stop at one end and a key-like male portion at its forward tip. A barrel-type combination lock forms an enlarged head and locks over the rod's forward shackle.
U.S. Pat. No. 4,711,106 to Johnson is another example of a prior art pin locking device. The disclosed device includes a stud having a threaded axial hole extending rearwardly from the forward end thereof and a keyed portion. A knob locks over a forward position of the stud and includes a casing with an inner surface that has a keyway. The keyway receives the corresponding key on the stud to prevent rotation of the casing with respect to the stud. The knob also includes a tumbler housing that is mounted in an axially fixed position within the casing to rotate freely when a key is inserted into the tumbler housing, and to remain locked in a fixed position when the key is withdrawn.
Similarly, U.S. Pat. No. 5,284,038 to Johnson discloses a pin locking device that includes a threaded stud with a flat face cut through the threaded surface. The flat face is parallel to the axial direction of the stud. The device also includes a knob that locks over a forward section of the stud and includes a casing having an inner surface that defines a hole extending axially through the casing. The inner surface of the casing has a flat surface extending axially that receives the corresponding flat face on the threaded stud to prevent rotation of the casing with respect to the stud. The knob also includes a tumbler housing that is mounted in an axially-fixed position within the casing to rotate freely when a key is inserted into the tumbler housing, and to remain locked in a fixed position when the key is withdrawn. Fitted into the rearward end of the tumbler housing is a sleeve having a threaded axial hole that engages the threaded stud when the tumbler housing is turned by a key to thereby pull the forward section of the stud into the casing hole.
U.S. Pat. No. 5,197,314 to Stillwagon et al. describes a prior art locking mechanism for a door latch. The mechanism comprises a post and collar gripping and release mechanism cooperatively mounted to the door and the door frame of a vending machine, cabinet, or the like. The mechanism provides an initial latching function in the form of a frictional gripping of the post by the collar. The locking mechanism further comprises a lock assembly associated with the post and collar mechanism to provide a primary locking function and to effect release of the latching function.